Many modern communication networks employ optical transmission of data packets. The main advantage of optical transmission is almost unlimited bandwidth, which allows transmitting data at high rates. Data is divided into packets, each of which contain information that should be delivered to a destination, and a header that contains the routing data. The routing data comprises address information which is used to route the data through a series of switching nodes to its destination. Each switching node decodes the address information by processing the header information and switching the packet onto a proper communication link (usually using a routing table that is stored in each switching node). The same procedure is repeated at the next node and so forth, until the packet reaches its destination.
Conventional routing methods of data packets in optical networks employ electrical processing of the header information, which is carried out at each switching node. However, due to hardware limitations such electrical processing is performed in a relatively low rate, and therefore the “decision” made at each switching node, through which communication link to forward each packet is delayed. Therefore, the overall delay time of each delivered packet from source to destination is increased.
U.S. Pat. No. 5,253,250 discloses an apparatus for switching of high speed optical data with the header information transmitted separately on a sub-carrier frequency. The header information is sub-carrier multiplexed with the data packet and is then transmitted at a lower rate than the information frame rate, so as to allow header processing by less expensive receivers. However, the data packet is delayed by an optical buffer for the time required for the switch to process the header information.
European Patent Application EP 794683A2 discloses an optical ATM self-routing switching system with reduced routing header bits. The switching system comprises a plurality of interface means responsive to an incoming ATM cell for producing an optical ATM cell containing a routing bit located in a time slot corresponding to the its destination. This allows to reduce the optical header bits and improve the data throughput. However, the remaining bits in the header are still electrically processed and therefore the routing of the optical information data is delayed.
U.S. Pat. No. 5,912,753 discloses an optical network in which a packet is routed by performing a logic operation between an address word carried in its header and a predetermined discriminator word. A routing decision is made according to the result of the logic operation. However, the logic operation is performed by electrically processing and therefore the routing of the optical information data is delayed.
U.S. Pat. No. 5,617,233 discloses a transparent optical node (TON) structure for use in optical packet switching architecture. Routing is performed by using a separate wavelength to carry the header information. The header portion of the packet is removed from the data portion and can be rewritten before reinsertion. Still, even only the header portion requires processing time to determine the desires routing decision, and therefore delays the packet routing.
U.S. Pat. No. 5,982,516 discloses an optical network in which data signals are encoded with a wavelength that corresponds to the destination address, so that data is routed in accordance with which of the switch characteristic wavelengths, matches the data encoding wavelength.
All the methods described above have not yet provided satisfactory solutions to the problem of providing method and apparatus for routing high speed optical data by using an optical routing address.
It is therefore an object of the present invention to provide a method and apparatus for routing high speed optical data, which overcome the drawbacks of prior art.
It is another object of the present invention to provide a method and apparatus for routing high speed optical data by using a control header which comprises an optical routing address that is transmitted optically.
It is another object of the present invention to provide a method and apparatus for routing high speed optical data by using an optical routing address which requires simple electrical processing.
Other objects and advantages of the invention will become apparent as the description proceeds.